1. Field of the Invention
The present invention relates to a sealing device, and more particularly to a sealing device for a collet chuck.
2. Description of Related Art
A tensioning nut is applied for fixing a collet chuck on a collet chuck housing. In use, the collet chuck is inserted into the collet chuck housing, and a tool shank is inserted into the collet chuck. The tensioning nut is mounted around the collet chuck housing and the collet chuck. When the tool shank is operated at high speed, such as for cutting or grinding an object, a temperature of the tool shank gets high. In the meantime, a coolant has to be poured from a back end of the collet chuck into the tensioning nut and the tool shank to cool down the tool shank to keep the temperature of the tool shank from getting too high.
With reference to U.S. Pat. No. 7,140,616 B1 and Germany Patent Number G 92 07 833.8, a conventional sealing device for the collet chuck comprises a tensioning nut, a sealing washer, and a sealing ring. The tensioning nut comprises a nut space. A front end of the nut space is formed as a stepped structure. The sealing washer is mounted in the nut space and corresponds to the stepped structure. A minor ring is mounted between the sealing washer and the tensioning nut. The sealing washer comprises a tool shank hole and a ring groove. The tool shank hole is formed through the sealing washer. The ring groove is formed concaved in the sealing washer. The sealing ring is mounted in the ring groove.
When the tensioning nut is mounted around the collet chuck and the collet chuck housing, the sealing ring abuts the tool shank to achieve a leak-proof effect for the coolant. The sealing ring abuts the tool shank by a pressure from the coolant from all directions, such that the coolant is kept from leaking out of the tensioning nut. However, the sealing ring is not positioned in the ring groove, which may lead to leak of the coolant.
When the amount of the coolant poured into the collet chuck and the tool shank is insufficient, the pressure of the coolant may be insufficient to press the sealing ring. The concussion caused by the tool shank in operation may displace the sealing ring from the surface of the tool shank. When the sealing ring is displaced from the tool shank, the coolant flows between the tool shank and the sealing ring, and then flows out of the tensioning nut. Therefore, the amount of the coolant poured into the tool shank will be decreased again, and the cooling effect for the tool shank will be degraded.
On the other hand, when the amount of the coolant poured into the collet chuck and the tool shank is sufficient, the pressure of the coolant is adequate to press the sealing ring on the surface of the tool shank. Nevertheless, when the coolant flows into the ring groove, the impact from the coolant may displace the sealing ring relative to the tool shank since the sealing ring is not positioned in the ring groove. When the sealing ring is displaced, the coolant may flow between the sealing ring and the tool shank, and then flow out of the tensioning nut. Therefore, the amount of the coolant that should have been poured into the tool shank to cool down the tool shank is decreased, so the cooling effect for the tool shank is degraded.
In particular, after prolonged use of the sealing device, the elasticity of the sealing ring is degraded, and the leakage as described above occurs more frequently.